RN: Add warning on the mask/unmask behaviour with view flattening (#14203)

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Stresses out that the mask/unmask components may not behave as expected
with view flattening

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Author: antonis

docs/platforms/react-native/session-replay/privacy/index.mdx

@@ -5,7 +5,7 @@ notSupported:
 description: "Learn how to mask sensitive data that may appear in your app in Session Replay."
 ---
 
-<Alert>
+<Alert level="warning">
 
 Using custom masking in your Session Replays instead of our default settings, may accidentally expose sensitive customer data. Make sure to test your app thoroughly to ensure that no sensitive data is exposed before publishing it.
 
@@ -118,3 +118,9 @@ The `Mask` and `Unmask` components are native on iOS and Android and are compati
 The masking components behave as standard React Native `View` components.
 
 If you're experiencing issues with unmasking that are more than one level deep, check if the wrapped components are present in the native views hierarchy. If not, it means that your view was evaluated by React Native as `Layout Only` and flattened. Read more about [flattening views](https://reactnative.dev/architecture/view-flattening) in the React Native documentation.
+
+<Alert level="warning">
+
+Note that [View Flattening](https://reactnative.dev/architecture/view-flattening) may cause the `Mask` and `Unmask` components to not behave as expected accidentally exposing sensitive data. Make sure to test your app thoroughly to ensure that no sensitive data is exposed before publishing it.
+
+</Alert>